1. Field of the Invention
The present invention relates generally to the field of prosthetic devices for use within a body passageway or duct and, more particularly, to the area of transluminally placed endovascular grafts prosthesis which are particularly useful for repairing blood vessels narrowed or occluded by disease.
2. Description of the Prior Art
Transluminal endovascular grafting has been demonstrated by experimentation to present a possible alternative to conventional vascular surgery. Transluminal endovascular grafting involves the percutaneous insertion into a blood vessel of a tubular prosthetic graft and its transluminal catheter placement at the desired location within the vascular system. Advantages of this method over conventional vascular surgery include obviating the need for surgically exposing, incising, removing, replacing or bypassing the defective blood vessel.
Despite the major advantages afforded by transluminal endovascular graft placement, this method inherently presents certain problems. During placement the graft prosthesis must be smaller than the lumen of the blood vessel through which it is moved by a catheter into the desired location. Since the lumen of the initially narrowed segment of blood vessel should, after graft placement, be approximately equal to that of the adjacent undamaged portions, it is necessry that the graft be increased in diameter after placement.
Another problem concerns the possible migration of the graft after placement at a desired location. Thus, the graft must be provided means for permanently anchoring in place.
Through previous experimentation, I have shown that the use of an expandable tubular coilspring prosthesis provides means for controlling the size of the prosthesis to facilitate placement and anchoring. The use of such a prosthesis was described in my following publication: Dotter, C. T.: Transluminally-placed Coilspring Endarterial Tube Grafts, Investigative Radiology, Vol. 4, No. 5, Sept.-Oct., 1969. As disclosed in this publication, the coilspring endovascular prosthesis can be either stretched out or wound up and hooked to a controlling mandrel so as to reduce the diameter of the prosthesis for easier introduction and placement. After placement and upon externally-effected release from the mandrel, the coilspring prosthesis automatically expands to provide a larger lumen and better anchoring at the site of placement.
The use of spring force to expand the diameter of a coilspring prosthesis after vascular placement presents a disadvantage to the degree that is unnecessarily complicates the grafting procedure, requiring increased skill of the physician in effecting implantation and also requiring a fairly complicated mechanism to effect external release from the mandrel. Thus, it would be desirable to employ a simpler method for externally controlling the diameter of the prosthesis within the body.
One type of graft prosthesis which is expandable within a blood vessel is disclosed in U.S. Pat. No. 4,140,126 to Choudhury. This refers to an elongated tube having a plurality of longitudinal folds interspaced with a plurality of radially spaced anchoring pins and mounted upon upper and lower expansion rings. The elongated tube is mechanically expanded by release of the upper and lower expansion rings. This device is characterized by a relatively complicated mechanical means for expanding the prosthesis within the blood vessel and is not adaptable for use as a prosthetic graft to repair an occluded segment of a blood vessel.
U.S. Pat. No. 4,130,904 to Whalen discloses a prosthetic blood conduit which includes a helically formed coil. The device is otherwise different than the present invention and is not adapted for implantation within an occluded blood vessel.
U.S. Pat. No. 3,713,175 to Weisman discloses a cobalt-chromium-tungsten-nickel-molybdenum alloy cardiovascular implant device. The allow is not disclosed to have shape memory properties and the implant is not temperature expandable for implantation purposes.
U.S. Pat. No. 4,159,719 to Haerr and U.S. Pat. No. 4,183,102 to Guiset both disclose devices which are expandable within a body duct, but are otherwise different from the present invention.
Accordingly, it is an object of the present invention to provide an improved graft prosthesis for therapeutic use within a body passageway or duct.
It is a further object of this invention to provide a prosthetic graft which is temperature expandable for opening or repairing body passageways or ducts, but which is inert to normal body temperature fluctuations.
These and other objects and advantages of the present invention will be apparent from the following description.